1. Field of the Invention
The present invention relates to a lip-type seal to be used to seal the outer circumference of the rotating shaft of a compressor which is used, for example, in an air conditioner.
2. Description of the Related Art
Conventionally, a lip-type seal of this kind comprises two seal members and includes a first seal member made of elastomer and a second seal member made of synthetic resin. The first seal member prevents refrigerant in a hermetic space or the like from leaking around the circumference of the shaft during rotation of the shaft. The second seal member not only functions as a negative pressure seal against the atmosphere when the pressure in the hermetic space becomes negative, but also supports a cylindrical part of the first seal member when the pressure in the hermetic space becomes high. In a configuration in which the second seal member supports the first seal member directly, the second seal member is pressed forcibly against the rotating shaft via the first seal member when the pressure in the hermetic space becomes higher than a predetermined value. As a result, the problem, in that a plastic deformation or cracks are generated due to frictional heat and leakage is caused, may occur. Moreover, since the first seal member is also pressed forcibly against the rotating shaft, a problem of excessive abrasion may also occur.
In order to solve these problems, a lip-type seal of the type in which the first seal member is supported by a rigid reinforcement member so that the pressure from the hermetic space side is not applied to the second seal member, has been presented. For example, a lip-type seal as shown in FIG. 6 has been disclosed in Japanese examined utility model publication (Kokoku) No. 2-47311.
The lip-type seal comprises a first seal member. 90 placed on the hermetic space A side, a second seal member 92 placed on the atmosphere B side opposite the first seal member 90 and an reinforcement member 91 which is placed between the first seal member 90 and the second seal member 92 and supports the atmosphere side of the first seal member 90. The reinforcement member 91 extends beyond the front end of the second seal member 92 as far as the hermetic space A side. In addition, the front end of the lip of the first seal member 90, which is pressed to and comes into contact with the rotating shaft, is not supported by the reinforcement member 91.
The hermetic space side of a lip-type seal is referred to as xe2x80x9cfront sidexe2x80x9d hereinafter.
In Japanese unexamined utility model publication (Kokai) No. 4-134962, a lip-type seal such as that shown in FIG. 7 has been disclosed. The lip-type seal comprises a forming ring (reinforcement member) 93, which covers the surface of the hermetic space A side of the first seal member 90 as far as the front end of the first seal member 90.
Moreover, in Japanese unexamined patent publication (Kokai) No. 6-58426, a lip-type seal such as that shown in FIG. 8 has been disclosed. In the lip-type seal, a thin sliding film 94 is formed at the front end of the first seal member 90. A reinforcement member 95 is attached so as to cover the hermetic space A side of the first seal member, excluding the sliding film 94;
In the lip-type seals disclosed in Japanese examined utility model publication (Kokoku) No. 2-47311 and Japanese unexamined patent publication (Kokai) No. 6-58426, however, reinforcement members 91 and 95 do not extend as far as the front end of the first seal member 90, so that a problem, in that parts of the front end of the first seal member 90, which are not covered by the reinforcement members 91 and 95 are deformed significantly and abrasion occurs when the pressure in the hermetic space A exceeds a predetermined value, appears.
In the lip-type seal disclosed in Japanese unexamined utility model publication (Kokai) No. 4-134962, since the rigid reinforcement member 93 covers as far as the front end, a problem, in that the first seal member 90 cannot adapt to the eccentricity or bias of the rotating shaft against the seal and sealing performance is deteriorated or abrasion of a partially contacted part develops quickly when the center of the rotating; shaft is biased from the center of the seal due to the error in attachment of the lip-type seal to the rotating shaft etc., may occur.
Moreover, since the reinforcement members 91, 93, and 95 in these conventional examples are made of rigid material, they do not have ability to adjust the contact force of the first seal member 90, and sealing performance is deteriorated if the tension is decreased due to the abrasion of the first seal member 90.
Recently, carbon dioxide gas has been considered for use as refrigerant gas, instead of fluorocarbon gas, in a compressor, but if carbon dioxide is used as refrigerant gas, there is the possibility that the pressure in the hermetic space is increased several times, and the above-mentioned problems become more conspicuous.
The present invention has been developed with above-mentioned problems being taken into consideration, and the purpose is to provide a lip-type seal which can suppress excessive abrasion by applying appropriate tension to the first seal member in a high pressure condition so as to suppress excessive deformation.
To realize the above-mentioned purpose, in the first aspect of the present invention, the lip-type seal comprises a first seal member, which is placed on the hermetic space side, made of elastomer and formed into an annular shape, and a second seal member, which is placed on the atmosphere side opposite the first seal member and radially inside of the first seal member, made of synthetic resin and formed into an annular shape, and the main target is that a nearly annular flexible reinforcement member of which the bending strength is higher than that of the first seal member is attached to the first seal member so that the reinforcement member extends as far as the end of the hermetic space side of the first seal member and at the same time, the first seal member is located at least radially inside the reinforcement member. Therefore, according to the present invention, an appropriate tension, which is generated by the inner pressure of the hermetic space side, can be applied to the first seal member while excessive abrasion by deformity can be suppressed.
In the second aspect of the present invention, the main target is that a retention member is provided between the first seal member and the second seal member to suppress deflection of the part of the first seal member opposite the second seal member in the radial direction, in the first aspect. Therefore, according to the present invention, in addition to the effect of the first aspect, interference of the first seal with the second seal member can be surely prevented even when the first seal member is deflected.
The present invention may be more fully understood from the description of the preferred embodiments of the invention, as set forth below, together with the accompanying drawings.